Electric heating – Heating devices – Combined with diverse-type art device
Reexamination Certificate
2000-05-31
2001-02-06
Hoang, Tu Ba (Department: 3742)
Electric heating
Heating devices
Combined with diverse-type art device
C219S202000, C219S212000, C219S528000
Reexamination Certificate
active
06184496
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to flexible heating mats for melting snow and ice on driveways, walkways, including stairs, and roofs.
2. Description of Related Art
Over the years there have been a number of attempts to melt snow and ice accumulations by heating the affected surface. Most past configurations required a permanent installation of the heating element inside the surface, as exemplified by Watanabe in U.S. Pat. No. 5,605,418 and Deschenes in U.S. Pat. No. 4,564,745. These solutions however tend to be expensive, are not readily adaptable to existing surfaces, and maintenance and repair often require destruction and reconstruction of the protected surface.
Several attempts at melting snow and ice accumulations by placing a heater on the surface of the area to be cleared have been made, as discussed below. Bayless et al., U.S. Pat. No. 4,967,057 teaches the use of multiple individual panels to cover varying size areas. The Bayless patent however calls for multiple connections between the separate panels, presenting potential failure points. Additionally the panel may be dislocated or disconnected when driven upon. Bayless also requires a large number of panels to cover large areas and thus is not desirable for installation on driveways. In fact, Bayless discloses that the panels are appropriate to steps and walkways only.
Another attempt by Shields, in U.S. Pat. No. 5,591,365 addresses those concerns by placing the heating element in a flexible lattice form. However, Shields uses a single series resistive element in the form of specialized and expensive heating cables distributed throughout the lattice. The use of a single series heating element prevents field customization of the heater to fit varying length of protected areas, and reduces reliability since a break in any point along the heater will render the whole apparatus inoperative.
Similar patents include U.S. Pat. No. 5,614,292 to Saylor, U.S. Pat. No. 5,003,157 to Hargrove, U.S. Pat. No. 3,806,702 to Spencer, and U.S. Pat. No. 5,637,247 to Flynn, Jr. Patents, such as U.S. Pat. No. 3,900,654 to Stinger have described heater elements allowing trimming to any desired length, comprising a thin, flexible laminated assembly of electrically conductive elastomeric material. U.S. Pat. No. 4,523,085 to Grise teaches flexible sheet film heating elements that comprises current feed electrodes, heretofore referred to as bus bars, disposed in parallel along two sides of the heater film. Multiple resistive ink patterns traversely connect between the bus bars to form an array of parallel connected heater elements. This arrangement allows for field customization of the heater length since the film heater may be cut anywhere between the parallel connected heating elements. However the Grise heater is not durable enough to sustain people or vehicular traffic or prolonged exposure to elements such as ultraviolet light, ozone, sand and chemicals. Additionally when cut, the Grise heater does not offer submersion protection since the bus bars are exposed at the cut end.
All the above, taken individually or in combination do not teach the current invention as claimed. An inexpensive solution to the problem of snow removal by electrical means that is easy to install by untrained personnel, and that may be sold in roll form to allow cutting for any desired length in the field is therefor clearly highly desirable and is presented in the instant invention.
SUMMARY OF THE INVENTION
The present invention is a heating mat for melting snow and ice. It has at least one planar flexible electric heater, each of which includes a first elongated, flexible, electrically insulating substrate which has an electrically insulated surface.
The planar flexible heater further includes a plurality of resistive heating elements comprising a plurality of resistive material traces deposited on the first insulating substrate in a spaced apart relationship. In addition, a first and second electrical conductor is each disposed in proximity to each of respective opposing edges of the electric heater, and a third electrical conductor is disposed at an intermediate location between the first and second electrical conductor. Each of the resistive material traces are in electrical communication with the first, second and third electrical conductors and extend therebetween.
In another embodiment, in lieu of applying a plurality of parallel resistive traces, a uniform layer of resistive material trace is applied to the surface of the first insulating substrate.
The planar flexible heater further includes a second elongated, flexible, electrically insulating substrate having an electrically insulated surface, wherein the first insulating substrate is adhesively attached to the second insulating substrate with the resistive elements and electrical conductors disposed therebetween. The first insulating substrate and the second insulating substrate form the flexible electric heater's two opposite planar surfaces.
The flexible electric heater is sandwiched between two protective sheets composed of abrasion resistant flexible material. Each protective sheet has an inner surface oriented towards and in face to face adherent engagement with the respective planar surfaces of the flexible electric heater. The two protective sheets and electric heater disposed therebetween form the heater mat which has two opposing end edges, and two opposing side edges.
A novel advantage of the present invention is that the resistive heating traces and electrical conductors are arranged such that a portion of the heating mat may be removed or cut away to accommodate a use by cutting the heating mat to remove an unwanted or interfering portion. With a portion of the heating mat cut away, the heating mat nevertheless is capable of maintaining its electrical operative characteristics despite removal of the cut away portion of the heating mat.
In another embodiment of the present inventive heating mat, the planar flexible heater may further include a grounding metallic substrate which is in a laminar relationship with the first insulating substrate. The grounding metallic substrate is adhesively attached to the first insulating substrate.
Each of the first, second and third electrical conductor is typically an elongate strip made of copper or a copper alloy. In a preferred application of the present invention, where a copper strip may be relatively stiff and may cause some separation between the conductor and the resistive material traces when flexing the heater, an elongate conductive film may be disposed between each of the first, second and third electrical conductors and the first insulating substrate. The elongate conductive film may be a thin layer or coating of silver or a silver alloy.
A practical way to bond the respective inner surfaces of the protective sheets onto the respective planar surfaces of the electric heater is by spraying a pressure sensitive hot melt adhesive on one of the respective planar surfaces of the electric heater or on one of the corresponding mating inner surfaces of the protective sheets.
Because the present invention is intended to be used on driveways, in such applications, it is preferred that at least one of the protective sheets includes an outer surface with a nonskid pattern impressed thereupon. For example, a nonskid pattern may include a plurality of ribs protruding therefrom, wherein the ribs form a cyclic V-pattern extending transversely to the side edges of the heating mat and the ribs further form drainage channels in the spaces therebetween. Such a pattern is commonly referred to as a “Chevron” pattern. Of course, other patterns may be used, including a straight transverse oriented V-pattern or a series of random embossed raised portions like that found in safety diamond plate. Such non-skid patterns would not be necessary when the present invention is installed on roof edges at or near the shingle drip edge flashing. Further, in some applications, the non-skid pattern may not be necessary for some s
Clearpath, Inc.
Hoang Tu Ba
LaPointe Dennis G.
Mason & Associates, PA
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